I'm thinking the single best thing you can do is keep it in a garage, especially if attached to the house, to moderate the temperature extremes. I've also read that not letting it sit at 100% charge for long times is better; I'm probably going to shoot for low 40s or one bar down in general, but I'm not going to be fanatical about it. I'm retired so I don't have a daily commute anymore, so 90% of the time 25 miles is all I'd need.
Not to anthropomorphize a battery, but it makes 'common' sense to me that not letting sit at 'max storing strain' all the time may be better. So I'm probably not going to be plugging it in every night 'just because', unless it's below about 35 I'll just go with it unless I know I have a long trip the next day--I do have a 50-mile trip each way once a week. I think that once-a-week HV mode, maybe an hour in total, will probably be good for the car in the long run.
Ben, you are correct that repeated cycles of max charging and full depletion are not only harmful, but will destroy a Li-ion battery. However Honda (as all EV mfg’s) has built into their Battery Management System (BMS) a buffer or cushion at the top and bottom ends of the state of charge (SOC) for this very reason.
This is why you see 2 bars when the EV ranges goes to 0 and the car enters HV mode. At this point you have deleted all the
usable charge allowed and the 2 bars indicates the buffer charge remaining to protect the battery from being completely discharged.
Similarly, here is a buffer at the top end of the SOC to do what you are proposing to do manually.
How do we know this since it’s not in the manual?
The most anyone has reported their EVSE has delivered to the Clarity’s on board charger is 14.1 to 14.4 kW. You must then take into account the loss to heat by the on board charger not being 100% efficient. If you assume a 90% efficiency (I’ve seen assumptions of 85-95%), then the 17 kW battery is only being charged approx. 12.5 to 13 kWs. Thus the amount of buffer seems to be 4-4.5 kW or about 24 to 27% roughly. This is on par with reports of the Volt and Tesla BMS from their forums. What we don’t know is how that total buffer is split between the top and bottom.
So, is trying to “baby” the battery necessary? Probably not.
But will it make the battery last longer, ie have a higher SOC as it ages?
Possibly, and here is where the assumptions and conjecture enter in.
Certainly it can only help and not hurt to do this, but my gut feeling is that it won’t affect the battery longevity by more than a very few percent so it’s not worth it to me. This is because Honda is already using a buffer to keep from fully charging the battery pack.
Guess we’ll just have to compare notes in 8-10 years ans see whose Battery Capacity Signal is higher.
One caveat: Several have theorized this the BMS does battery cell balancing when the battery is charged to its full usable capacity, ie until charging stops. Supporting this theory is that the manual stating to fully charge before driving. So if you implement your strategy, it would be prudent to periodically fully charge.
